The Google Wave documentation contains the Robot Events, but doesn't list what values will be put into the properties dictionary. Is this documented anywhere?
I had the same question and found some hints in the following Google group thread: http://groups.google.com/group/google-wave-api/browse_thread/thread/8d19dbcb6f2147cc
For now, I think the closest you can get to an answer to this question is Jason Salas' response: "the good news is that you can look in the logs that Google App Engine generates for your robot in your dashboard (choose Info from the drop-down menu under your application), and you can manually read the JSON string and get the "properties" content."
I guess we'll just have to wait until the API stabilizes and the documentation is more complete.